Japanese Laid-open Patent Publication No. 2001-144449 discloses a technology in which thermally-conductive resin is loaded between an electronic component and a planar thermal conductor, and the loaded state of the thermally-conductive resin may be checked through a check hole. With this technology, heat generated at the electronic component is made to escape to the planar thermal conductor via the thermally-conductive resin. Japanese Laid-open Patent Publication No. 2004-222426 discloses a technology in which a submarine apparatus is provided with a layer formed of a thermally-conductive mesh material between an internal unit and an external housing. With this technology, heat generated at the internal unit is made to escape to the external housing via the thermally-conductive mesh layer.